Refrigerant expansion control



Oct. 9, E. L. SCHULZ ETAL REFRIGERANT EXPANSION CONTROL Original Filed Feb. 2, 1946 INVENTOR.

2,7 65,629 REFRIGERANT EXPANSION CONTROL Edward L. Schulz, Pittsburgh, Pa., and Edward A. Bailey, Auburn, N. Y., assignors to Carrier Corporation, Syracuse, N. Y., a corporation of Delaware Original application February 2, 1946, Serial No. 645,183, new Patent No. 2,614,393, dated October 21, 1952. Divided and this application September 12, 1952, Serial No. 309,206

Claims. (Cl. 62-3) now Patent No. 2,614,393, granted October 21, 1952, and relates to the art of refrigeration and more particularly to control arrangements for regulating the production of refrigeration effect, the control arrangements being responsive to variations in load conditions and being adapted to compensate for overload conditions arising from unforseen causes. If desired, the control arrangements may be designed to respond to variations in load as indicated by the temperature of the area being served to compensate for conditions of underload.

The general object of the invention in to provide simple and effective control arrangements for regulating the action of an expansion valve to compensate automatically for conditions resulting in undesirable condenser pressures or suction pressures.

A feature of the invention resides in the provision of a metering arrangement in the high side of a refrigeration system for reducing the rate of admission of refrigerant to an evaporator or cooler When the condenser pressure exceeds a predetermined maximum.

Another feature of the invention resides in the provision of a refrigeration system including means connecting the discharge line and the exit end of the evaporator, and control means, which upon an increase in condenser pressure above a predetermined maximum, permits'liquid refrigerant to flow into the suction line to aifectthe bulb controlling operation of the expansion valve thereby causing the expansion valve to throttle the flow of refrigerant to the evaporator or cooler.

Another feature of the invention resides in the provision of a metering arrangement in the high side of a refrigeration system for increasing or decreasing the rate of admission of refrigerant to an evaporator or cooler when the temperature of the area being conditioned varies from a predetermined standard, such metering arrangements being combined with or in addition to control means responsive to condenser pressure. Other features of our invention will be readily perceived from the following description.

In the operation of refrigeration systems, it is usual to employ an expansion valve for maintaining a desired predetermined super-heat at the exit or discharge end of the evaporator; the valve is usually set to provide a superheat of 12 to 15 as may be desired.

The expansion valve tries to maintain this degree of super-heat in the suction line regardless of any undesirable situation such as excessive head pressure which may develop in the rest of the system. This is true particularly of liquid charged expansion valves. However, gas charged expansion valves do limit excessive head pressure to a certain extent since they remain closed until the suction pressure drops below a certain predetermined point depending on the charge of the thermal bulb. These types of expansion valves do not protect the rest of the system against the effect of excessive headpressure caused by unusual conditions such as excessively high ambient 2,765,629 'l"?atentetl Oct. 9, 1956 temperatures, dirty condenser surface, or break-down of the cooling system. A conventional refrigeration machine is usually protected against such conditions by a high pressure switch which stops the refrigeration machine. This gives protection but at the same time cuts off all refrigeration and hence the use of such device per se is undesirable and unsatisfactory.

This invention is designed to obviate such undesirable conditions by reducing the amount of refrigerant admitted to the evaporator to that which can safely be handled by the compressor. As a result, regardless of deficiencies in operation of the condenser, or regardless of load conditions affecting the system, the control arrangement will enable the system to function effectively with maximum utility having due regard for such impairment as may aifect the operation of any of the component parts.

The control arrangements of the present invention are directed to simple and inexpensive means of modulating the action of an expansion valve or supplementing the operation of an expansion valve to limit the quantity of refrigerant flowing through the evaporator to that Which can be handled safely by the compressor without overload.

The attached drawings illustrate a preferred embodiment of our invention in which:

Figure 1 is a diagrammatic view of a refrigeration system illustrating a preferred embodiment of the present invention;

Figure 2 is a diagrammatic view of a control valve for use in the system shown in Figure 1;

Figure 3 is a fragmentary diagrammatic view illustrating a modified form of the invention shown in Figure 1;

Figure 4 is a second'fragmentary diagrammatic view illustrating a further modification of the invention shown in Figure 1; and

Figure 5 is a diagrammatic view of the control valve for use in the system shown in Figure 3.

Referring to the drawings there is shown a compressor 2 of the reciprocating type, although it may be of any desired type, adapted to discharge compressed refrigerant gas through line 3 to a condenser 4. Condenser 4 may be air or water cooled as desired; condenser 4 is illustrated as air cooled by means of fan 5. Condensed refrigerant enters receiver 6 and then proceeds through discharge line 7 to control valve 8, expansion valve 9 and evaporator 10, returning to compressor 2 through suction line 11. Expansion valve 9 operates in the usual manner under control of bulb 12 attached to the discharge side of evaporator 14 to maintain a predetermined super-heat in the refrigerant discharged from evaporator 19. As is customary, an equalizer line connects expansion valve 9 with suction line '11 to provide a pressure under the diaphragm of the expansion valve equal to the pressure at the discharge end of the evaporator.

When the system operates normally and the condenser pressure as reflected in line 7 remains below a predetermined upper limit of 200 pounds, for example, valve 8 remains fully open and the system operates as if valve 8 were omitted therefrom.

Assuming that the system becomes overloaded due, for example, to the break-down of fan 5, used for cooling the condenser (or due to the break-down of the water supply if the condenser depends upon water for refrigerant cooling purposes), then the pressure in condenser 4, receiver-6 and line 7 rises. If the failure to provide condenser cooling becomes so serious as to cause the pressure to rise above the predetermined maximum limit of 200 pounds in the example given, then damage to the system would result unless operation was stopped or the capacity of the system effectively reduced so that only that amount of refrigerant was handled which could be condensed effectively.

When the pressure in discharge line 7 (the'condensing pressure) exceeds the predetermined maximum of 200 pounds, control valve 8 will operate responsive to a rise in pressure above the set figure to decrease progressively the "amount of refrigerant permitted to enter evaporator through expansion valve 9. The volume of refrigerant admitted to evaporator 10 will decrease as the condensing pressure increases above the predetermined maximum of 200 pounds. If the fault in the system causing the increase in condensing pressure is due to impaired condensing action, but assuming some condensing action does take place, then valve 8 will permit a reduced quantity of refrigerant to be admitted to evaporator 10, such reduced volume being the maximum which the system can handle without a further increase in condensing pressure.

Assuming that a pressure of 200 pounds, for example, which is below the danger point would not be exceeded if only a portion of the normal volume of refrigerant is permitted to be circulated in the system, then control valve 8 will constrict the flow leading to expansion valve 9 and evaporator 10 so that only such percentage of the normal amount of refrigerant will be delivered by the system.

Since such operation at reduced efficiency is undesirable, suitable means may be provided for informing the operator of the abnormal conditions.

Obviously, under conditions of serious impairment, such as when fan 5 breaks down or when the supply of cooling fluid to a water cooled condenser is completely shut off, the system will be unable to function effectively even with a much reduced supply of refrigerant. In such case the pressure will rise above the danger point and control 13, which may be a simple, high pressure cut out control, well known in the art, will function to stop the operation of compressor 2, as by breaking an electric circuit to a motor operating the compressor.

For purposes of illustration, control valve 8 may take the form shown in Figure 2. Considering Figure 2, control valve 8 includes a housing 14 containing a diaphragm 15 disposed in position therein. A spring 16 is disposed adjacent one side of the diaphragm and is adapted to apply a predetermined force thereto. A stem 17 carrying valve member 18 is adapted to close a port 19 within housing 14. Under normal conditions spring 16 flexes diaphragm 15 downward moving stem 17 downward thus moving valve member 18 away from port 19, permitting free flow of refrigerant through entrance port 20 into the housing, through port 19 and through discharge port 21. As pressure increases in discharge line 7, force is exerted against diaphragm 15, flexing it in the opposite direction and raising stem 17 carrying valve member 18 to close port 19 to the required extent. As the condenser pressure again decreases, spring 16 flexes diaphragm 15 to move valve member 18 away from port 19 to open port 19 to the free passage of refrigerant.

If desired, in the system illustrated in Figure 1, control means may be provided as shown in Figure 3 for regulating the flow of refrigerant responsive to variations in load in an area served by the system. Such means may comprise a suitable diaphragm 22 incorporated in a control valve 8 (refer to Figure 5), which is actuated by a bulb 23 disposed preferably in the area being served. In such case a decrease in the temperature of the area being served will tend to move control valve 8 toward a closed position thus reducing theflow of refrigerant to evaporator 10. The decrease in temperature in the area being conditioned is reflected by bulb 23 which serves to apply pressure to diaphragm 22thus permitting control valve 8 to be urged toward a closed position.

For purposes of illustration, valve 8' may take the form shown in Figure 5. Valve 8' contains a diaphragm 22 disposed within the chamber therein. Diaphragm 22 separates the chamber 30 into two compartments 31, .32. Pressure in compartment 31 is controlled by bulb 23 while pressure may be applied against the opposite side of the diaphragm by spring 33. A stem 34 is secured to diaphragm 22 and carries a valve member 35 to close port 36 within the valve. Valves of this type are well known in the art.

In the structure shown in Figure 5, a bellows 37 is added which carries a lever 38 connected to a continuation 34' of stem 34. Lever 38 is hinged at point 39. An increase in pressure in discharge line 7 extends bellows 37 forcing lever 38 to pivot about point 39 to move valve member 35 upward to close port 36. A decrease in temperature of the area being served reduces the pressure in chamber 31 and permits spring 33 to urge valve member 35 upward to close port 36.

In a structure of the type contemplated, control valve 8 normally functions to restrict the flow of refrigerant in order to take care of conditions of overload. It may be actuated, however, as described above to compensate for conditions of underload; in such case, control valve 8 may be employed and actuated to compensate for a reduction in load as reflected by a reduction in temperature within the area being conditioned.

If desired, a second control valve 24 as shown in Figure 4 may be disposed in line 7 which may be actuated by a bulb 25 disposed in the area being served. Such valve operates similarly to the structure described above. A decrease in temperature in the area being conditioned, as reflected by bulb 25, urges control valve 24 toward a closed position to compensate for the reduction in load, thus decreasing the amount of refrigerant forwarded to evaporator 10.

The present invention provides a ready and simple control arrangement for regulating the production of refrigeration effect in response to variations in load conditions. The system so provided compensates for overload conditions arising from unforeseen causes. It provides a simple and effective control for regulating the operation of an expansion valve to compensate automatically for conditions resulting in undesirable condenser pressures. The control arrangement so provided is responsive to the pressure of the system, and if desired, may also be responsive to the temperature of the area being conditioned, thus assuring satisfactory results in operation. The control arrangement operates effectively to throttle the flow of refrigerant to an evaporator when condenser temperature rises above a predetermined maximum. The control arrangement provided effectively regulates operation of the system in response to conditions of overload or partial load.

While we have described and illustrated a preferred embodiment of our invention, it will be understood our invention is not limited thereto since it may be otherwise embodied within the scope of the following claims.

We claim:

1. In a refrigeration system, the combination of a compressor, a condenser, an expansion valve, and an evaporator disposed in a closed circuit including a discharge line, means in said circuit to regulate the quantity of refrigerant passing to the evaporator, said means being responsive to an increase in pressure in the discharge line above a predetermined level to decrease the quantity of refrigerant passing to the evaporator, and

means responsive to the temperature of an area being conditioned to regulate the quantity of refrigerant passing to the evaporator, said first means compensating for conditions of overload of the system and said second means compensating for conditions of partial load of the system.

2. In a refrigeration system, the combination of a compressor, a condenser, an expansion valve and an evaporator disposed in a closed circuit, and control means in the circuit placed between the expansion valve and the condenser responsive to an increase in condenser pressure above a predetermined level to regulate the quantity of refrigerant passing through the expansion valve to the evaporator, said control means upon an increase in condenser pressure above a predetermined level tending to close to limit the quantity of refrigerant passing to the expansion valve thereby compensating for conditions of overload of the system.

3. In a refrigeration system, the combination of a compressor, a condenser connected to said compressor, an expansion valve, a discharge line connecting the condenser With said expansion valve, an evaporator connected to said expansion valve, a suction line connecting the evaporator and the compressor, means disposed adjacent the suction line adapted to regulate the ca in response to the temperature of refrigerant the suction line, a control valve in the discharge line placed between the condenser and the expansion valve adapted to meter the quantity of refrigerant passing to the expansion valve, said control valve in response to an increase in pressure in the discharge line above a predetermined level tending to move toward a closed position to decrease the quantity of refrigerant passing to the expansion valve.

4. In a refrigeration system, the combination of a compressor, a condenser, an expansion valve and an evaporator disposed in a closed circuit, and a control valve in said circuit for regulating the quantity of. refrigerant passing to the expansion valve, said control valve being operable in response to an increase in condenser pressure above a predetermined level to move toward a closed position to decrease the quantity of refrigerant passing to the expansion valve and being responsive to a decrease in temperature of an area being conditioned to move toward a closed position to decrease the quantity of refrigerant passing to the expansion valve.

5. In a refrigeration system, the combination of a compressor, a condenser connected to the compressor, an expansion valve, a discharge line connecting the expansion valve with the condenser, an evaporator connected to the expansion valve, a suction line connecting the evaporator to the compressor, a bulb disposed adjacent the suction line for regulating the operation of said expansion valve, 21 control valve disposed in the discharge line for regulating the quantity of refrigerant passing to the expansion valve, said control valve being operable in response to an increase in condenser pressure above a predetermined level to regulate the quantity of refrigerant passing to the expansion valve, and means for regulating the quantity of refrigerant passing to the expansion valve in response to a variation in temperature in an area being conditioned.

References Cited in the file of this patent UNITED STATES PATENTS 1,238,051 Peterson Aug. 21, 1917 2,191,102 Zerk Feb. 20, 1940 2,304,316 Newton Dec. 8, 1942 2,311,622 Alexander Feb. 23, 1943 2,363,273 Waterfill NOV. 21, 1944 2,415,338 Carter Feb. 4, 1947 2,443,500 Goddard June 15, 1948 2,506,757 Wilson May 9, 1950 2,556,882 Minkler June 12, 1951 

